Approved Abstracts

Zn bioaccumulation modelling in the clam Ruditapes philippinarum from sunscreens in seawater

Author(s): Rodriguez-Romero A; Tovar-Sánchez A; Gaudron A; Ruiz-Gutiérrez G; Viguri Fuente JR;
Presenter: Javier R. Viguri Fuente

The presence of these products in the marine environment is increasing associated to the growth of coastal and sea tourism activities. Therefore the potential dangers to marine ecology caused by chemical UV filters, both organic and inorganic, which are main components in the formulation of sunscreens, is a cause of concern. The present work aims to model the bioaccumulation kinetics of Zn in clams of the species Ruditapes philippinarum exposed for a period of 10 days to four different concentrations of sunscreen: 5 mg/L, 50 mg/L, 100 mg/L, 200 mg/L. Seawater was renewed every 2 days and samples were taken in duplicate for analysis periodically. Experimental results of Zn concentration in clams were modelled using Aspen Custom Modeler software (Bedford, Massachusetts, USA), which simultaneously solves rigorous models and estimates parameters. A three-compartment model is proposed for description of Zn bioaccumulation kinetics in clams. The model assumes that Zn from sunscreen is distributed in two seawater compartments: Zn retained in the colloidal organic residues from the sunscreen (Compartment 1) and Zn soluble in seawater (Compartment 2). Zn from both compartments can be transferred to clams (Compartment 3). Zn concentrations in compartments 1 and 2 are assumed constant and with negligible impact on the bioaccumulation of Zn because its periodical renewal. A first-order kinetic is considered to the Zn mass transfer between proposed compartments, stating the mass balance at the Zn concentration in clam as:

d[Zn(t)]/dt=k_d LC [Zn(aq)]+k_o SC [Zn(org)]-k_e [Zn(t)] (1)

Eq. (1) describes the bioconcentration of Zn in clams (d[Zn (t)]/dt), by three additive terms that represent the increase in the Zn concentration in clams which comes from seawater, the one that comes from organic colloidal residues and the decrease of Zn concentration in the clam due to the excretion. A uptake rate coefficient, k_u, is defined as: k_u=k_d∙LC= k_d∙V/Mc, where V is the volume of seawater (L) and Mc is the dry mass of clams (g). Results show that Zn concentration in clams increases from 9.24 µg/g to 106 µg/g at 50 mg/L and 200 mg/L sunscreen additions respectively. Estimated values of the parameters k_u (L g-1 d-1) and k_e (d-1) ranged from 0.00762 to 0.204) and from 0 to 0.0871 respectively. Estimated value of k_o=0 was obtained for all sunscreen concentrations suggesting no Zn uptake in the clam tissues from organic colloidal residue.
This work provides a mathematical model that allows describing the bioaccumulation kinetics of Zn in clams present in seawater due to the addition of sunscreen. The model predicts sharp bioaccumulation rates at sunscreen additions up to 50 mg/L.

Financial Support: This work has been co-financed by the European Union under the 2014-2020 ERDF Operational Programme and by the Department of Economic Transformation, Industry, Knowledge, and Universities of the Regional Government of Andalusia (Project reference: FEDER-UCA18-106672). Dr Araceli Rodríguez-Romero is supported by the Spanish grant Juan de la Cierva Incorporación referenced as IJC2018–037545-I.

Keywords: Inorganic UV filters; metal release; bivalves




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